A compact all terrain vehicle is disclosed for instance in Japanese Unexamined Patent Application Publication 2006-027425. In this compact vehicle, an engine unit equipped with a V-belt type automatic transmission is mounted below the seat, platform style footrests are arranged on the left and right sides of the seat, and a fuel tank is arranged below the seat. Furthermore, a portion of the fuel tank is located above the engine unit.
There is demand in the market for vehicles which have a compact body and are at the same time equipped with more sophisticated accessories of various types, such as an electronic fuel injection system and electrical power assisted steering. When an electronic fuel injection system is provided, a high pressure fuel pump would be arranged inside the fuel tank, but if a fuel tank with a built-in fuel pump is arranged below the seat, the width dimension of the vehicle's seat can easily become larger. Furthermore, with more electrically driven devices, the capacity of the battery that serves as a power source becomes larger, so its layout also needs to be considered. In the vehicle described in the aforementioned prior patent publication, the battery is arranged to the front of the steering handlebar. Furthermore, a portion of the fuel tank is located above the engine unit (crankcase) under the seat, so there is the problem that the seat width tends to become larger and space under the seat becomes more constricted and is hard to utilize efficiently.
Furthermore, an exhaust duct connected to the transmission case extends along the side of the fuel tank toward the rear of the vehicle, and this point also tends to make the width dimension of the seat larger.